For the dough, separate the eggs. Beat the egg whites with 50 g sugar until stiff. Beat the softened butter or margarine with the remaining sugar, vanilla extract and egg yolks until foamy. Mix and stir in the flour, cornflour and baking powder, fold in the egg whites. Spread the dough on the greased baking sheet and prebake for 10 minutes in a preheated oven on the middle shelf at 180 °C (upper and lower heat).

For the topping, pit the cherries or scrub, peel and cut the rhubarb into small pieces. Separate the eggs. Beat the egg whites with 60 g sugar until stiff. Beat the butter, remaining sugar, vanilla extract and egg yolks until foamy. Stir in the curd cheese and the cornflour mixed with the baking powder, fold in the beaten egg whites and cherries or rhubarb. Spread the topping over the pre-baked cake and bake for an additional 40 - 45 minutes. After cooling, dust with icing sugar as desired. 

Hint: 
Canned sour cherries may be used instead of fresh cherries.